Depends on how much power you pull out of it and the model. Every decent car in working order should be able to run at an idle witho AC and such running without

Depends on how much power you pull out of it and the model. Every decent car in working order should be able to run at an idle witho AC and such running without getting dangerously hot. But your intuition is correct, they aren't expecting to be outputting that much power without also getting additional airflow from moving. With a water cooled engine though all you really have to do in most cases is either put more fans on the radiator or hook up a larger radiator to increase cooling levels if the stock equipment can't keep up.